This invention relates to compositions for the sustained release of organic compounds.
The usefulness of many organic compounds, such as insecticides, herbicides, antimicrobials, fertilizers, medicines and the like, would be greatly improved if an inexpensive, effective system for the continual release of such compounds were available. Many organic compounds, for example, are volatile or unstable in the environment in which they are employed. When large doses of such compounds are used, much of the compound volatilizes or decomposes before performing its desired function. Accordingly, it would be desirable to administer such compounds in a form which reduces the rate of volatilization or decomposition thereof while maintaining effective levels of the compound in the system treated therewith. Other organic compounds are effective in very low concentrations, and are most effectively employed when such low effective concentrations are continually released into the system being treated. Moreover, the use of still other such compounds would be increased if they could be employed as a solid, such as a film or powder.
Various processes are known in which polymeric materials are employed in conjunction with organic compounds to form sustained release systems. For example, in U.S. Pat. Nos. 3,795,744 and 3,857,964, it is taught to form a coating of a polymeric material such as a cellulose ether around the organic compound to be released therefrom. The organic compound is released by the physical destruction of the polymeric coating or by the leaching of the organic compound through the polymeric coating. Unfortunately, due to the limitations in size and physical form of such coated compositions, the use thereof is greatly restricted. In addition, the coating operation must be carefully controlled in order to obtain a product having predictable and desirable release characteristics.
Another conventionally employed sustained release system comprises forming a solid matrix of a binder material such as a cellulose ether, which matrix has dispersed therein the organic compound to be released. While such matrix systems are somewhat useful in the preparation of pharmaceutical tablets, the size of such matrix systems often precludes the use thereof in other applications. In addition, the active agent is often unevenly distributed in such matrix systems, causing uneven release of the active agent.
Accordingly, an easily prepared sustained release system for organic compounds, which system has a physical form which is amenable to a variety of uses would be highly desired.